The present invention relates to an improved safety joint for use with a flowline, particularly to provide a connection for subsea pipeline to a subsea well to avoid transmitting loading, which is imposed on the pipeline by such outside forces as a ship's anchor, to the subsea well.
It is known that many times subsea pipelines are subject to large loads resulting from ships' anchors. Many times such loads tends to move the pipelines away from their axis, producing a torsional load on their connection to the subsea well.
One method of protecting against such loading is to ensure that the subsea structures are reinforced to withstand the expected loading This solution is quite expensive.
Another method is to design the flowline to part or fail in order to prevent this loading from being transmitted to a subsea well. One particular disadvantage to such prior attempted solutions is that which the joints are normally a pressure balanced in-line safety joint, they normally include non-metal sealing and thus include a number of elastomeric seals, one or more of which are potential leak paths to the environment.
A typical example of a pressure balances safety pipeline connector is disclosed in U.S. Pat. No. 4,059,288 in which the two tubular components are held together by a shear and by pins carried by the pressure compensating piston and held in engagement with an external recesses in the inner member by a ring. Upon initial movement following the shearing of the disc, the ring is moved to release the pins to move out of the recesses and allow complete release of the two joint members.
U.S. Pat. No. 4,059,288 discloses another pipeline safety joint including a fluid-tight pressure compensation chamber and held together by frangible bolts and a latch. When there is sufficient loading to cause the failure of the bolts, then there is sufficient movement between the two joint member to allow the latch mechanism to release and complete the disengagement between the two portions of the joint.
Another type of pipe coupling which includes a pressure compensating devices also includes one of two valves which close automatically on the separations of the joint is discloses in U.S. Pat. No. 4,361,165.
U.S. Pat. Nos. 3,502,353 (shear pins), 3,659,877 (shear bolts connecting flanges) and 3,727,948 (shear pins in on member engage threads in the other member) all disclose breakaway tubular joints.